clinical study effects of low-flow sevoflurane anesthesia...

Clinical StudyEffects of Low-Flow Sevoflurane Anesthesia onPulmonary Functions in Patients Undergoing LaparoscopicAbdominal Surgery

Cihan Doger,1 Kadriye Kahveci,2 Dilsen Ornek,3 Abdulkadir But,4

Mustafa Aksoy,4 Derya Gokcinar,2 and Didem Katar5

1Department of Anesthesiology and Reanimation, Ankara Ataturk Training and Research Hospital, 06800 Ankara, Turkey2Department of Anesthesiology and Reanimation, Ulus State Hospital, 06050 Ankara, Turkey3Department of Anesthesiology and Reanimation, Ankara Numune Training and Research Hospital, 06230 Ankara, Turkey4Department of Anesthesiology and Reanimation, Faculty of Medicine, Yildirim Beyazit University, 06800 Ankara, Turkey5Department of Pulmonology, Ankara Yenimahalle State Hospital, 06370 Ankara, Turkey

Correspondence should be addressed to Cihan Doger; [email protected]

Received 18 February 2016; Revised 18 April 2016; Accepted 31 May 2016

Academic Editor: Joshua Lawson

Copyright © 2016 Cihan Doger et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Objective. The aim of this prospective, randomized study was to investigate the effects of low-flow sevoflurane anesthesia on thepulmonary functions in patients undergoing laparoscopic cholecystectomy.Methods. Sixty American Society of Anesthesiologists(ASA) physical status classes I and II patients scheduled for elective laparoscopic cholecystectomy were included in the study.Patients were randomly allocated to two study groups: high-flow sevoflurane anesthesia group (Group H, 𝑛 = 30) and low-flowsevoflurane anesthesia group (Group L, 𝑛 = 30). The fresh gas flow rate was of 4 L/min in high-flow sevoflurane anesthesia groupand 1 L/min in low-flow sevoflurane anesthesia group. Heart rate (HR), mean arterial blood pressure (MABP), peripheral oxygensaturation (SpO

2), and end-tidal carbon dioxide concentration (ETCO

2) were recorded. Pulmonary function tests were performed

before and 2, 8, and 24 hours after surgery. Results. There was no significant difference between the two groups in terms of HR,MABP, SpO

2, and ETCO

2. Pulmonary function test results were similar in both groups at all measurement times. Conclusions. The

effects of low-flow sevoflurane anesthesia on pulmonary functions are comparable to high-flow sevoflurane anesthesia in patientsundergoing laparoscopic cholecystectomy.

1. Introduction

The use of the low-flow anesthesia technique provides pro-tection of the heat and humidity of the respiratory system,while minimizing cost and preventing air pollution. Thephysiology of the tracheobronchial environment is protectedas mucociliary clearance is more excellently maintained in alow-flow anesthesia technique than in high-flow anesthesia[1–4]. Moreover, as the waste gases are reduced, atmosphericpollution is lowered, health risks for operating room staff aredecreased, and ecological balances are maintained. However,possible disadvantages resulting from the inappropriate useof low-flow anesthesia include hypoxia, excessive or insuf-ficient concentrations of volatile agents, hypercapnia, and

the accumulation of potentially toxic gases. Low-flow anes-thesia is the issue before the Y piece as connection point withtube/circle system. That means that if low-flow anesthesiais used successfully in a patient, it will never have differenteffects on pulmonary functions in comparison with higherflow anesthesia. It only affects the waste gas amount normally.

Laparoscopic techniques compared with open surgeryare more widely preferred in the surgical field, because theyrequire a shorter hospital stay and cause less morbidity andmortality [5]. In laparoscopic surgery, the field of interestmaybe visualized by forming an artificial pneumoperitoneum.The pneumoperitoneum is created by insufflating CO

2into

the peritoneal cavity at a mean flow rate of 1-2 L/min.The pneumoperitoneum has both mechanical and chemical

Hindawi Publishing CorporationBioMed Research InternationalVolume 2016, Article ID 3068467, 5 pageshttp://dx.doi.org/10.1155/2016/3068467

2 BioMed Research International

effects on the pulmonary system. With the first insuffla-tion, intra-abdominal pressure is increased, causing thediaphragm to be distended upward.This distension increasesintrathoracic pressure, and the alveoli are collapsed. Duringthe laparoscopy, the direct effects of the additional positiveend-expiratory pressure cause a hemodynamic imbalance [5–7].

Few studies have explored the low-flow sevofluraneanesthesia technique for laparoscopic abdominal surgery. Inthis study, we aimed to investigate the effects of low-flowsevoflurane anesthesia on pulmonary functions in patientswho underwent laparoscopic cholecystectomy.

2. Methods

Approval for this study was obtained from the Ethics Com-mittee at the University of Yildirim Beyazit, Faculty ofMedicine, with number 2012-T4137-03-333. It conforms to theprovisions of the Declaration of Helsinki. Written informedconsent was obtained from all patients. Seventy patients(20–55 years old) scheduled to have elective laparoscopiccholecystectomy and classified as American Society of Anes-thesiologists physical status class I or II were prospectivelyenrolled. Patients with obstructive pulmonary disease andcardiac or renal or hepatic disease, smokers, and those fastingfor more than 12 hours were excluded. A web application(https://www.randomizer.org/) was used for randomization.Patients were randomly allocated to two study groups: high-flow sevoflurane anesthesia group (Group H) and low-flowsevoflurane anesthesia group (Group L). The patients wereblind to which group they were in, but the intraopera-tive anesthesia team were informed about anesthesia andmethod. But both postoperative pulmonology and anesthesi-ology doctor, who evaluated pulmonary function tests, wereblinded.

2.1. Anesthesia. All patients were premedicated with mida-zolam at a dose of 0.02mg/kg intravenously (IV) 30 min-utes before the operation. Heart rate (HR), noninvasivemean arterial blood pressure (MABP), peripheral oxygensaturation (SpO

2), and end-tidal carbon dioxide concentra-

tion (ETCO2) were monitored. All patients were induced

by fentanyl (1 𝜇g/kg IV) and propofol (3–5mg/kg IV)and muscle relaxation was achieved by administration ofatracurium (0.5mg/kg IV). Anesthesia was maintained at3.4% sevoflurane and 50% nitrous oxide in oxygen. Patientsin Group H received fresh gas flow of 4 L/min throughoutthe procedure. Patients in Group L received a fresh gasflow rate of 4 Lmin−1 for the first 10min and then weremaintained with a fresh gas flow of 1 L/min. All patients weremechanically ventilated with a tidal volume of 8mL/kg anda frequency of 12 breaths/min with the ventilatory (Drager�Julian, Lubeck, Germany) rate adjusted to maintain ETCO

2

of 30 to 40mmHg. Atracurium (10mg IV) was administeredevery 20 minutes. Hemodynamic functions were maintainedwithin 20% of baseline by adjusting supplemental fentanylinjection, as well as vasoactive drugs as needed. Sevofluranewas discontinued with the beginning of the skin sutures

and the fresh gas flow was changed to 6 L/min of oxygen.Neuromuscular blockade was reversed by administeringneostigmine (0.04mg/kg IV) and atropine (0.02mg/kg IV).The patient was extubated when the patient met the criteriafor tracheal extubation (respiratory rate >8, spontaneousbreathing with a minimum of 8mL/kg body weight, abilityto sustain a 5 s head lift, sustained hand grip, and sustainedarm lift). Fresh barium hydroxide was used to fill the carbondioxide-absorbent canister before each patient.

2.2. Measurements. Pulmonary function tests were per-formed before and after the surgery at 2nd, 8th, and 24thhours. Forced vital capacity (FVC, L), forced expiratoryvolume in 1 s (FEV1, L), and forced expiratory volume in1 s/forced vital capacity (FEV1/FVC%) values were measuredusing the spirometer (KoKo Legend 314000 Spirometer,nSpire Health, USA) by the same physician and the patientsperformed the forced expiratory maneuver at least threetimes in the sitting position. The pulmonary function testresults were expressed as percentages of the expected valuesadjusted for age, height, body weight, and sex [8]. HR,MABP,and SpO

2were monitored and recorded after tracheal intu-

bation and at 5min intervals during intraoperative period.ETCO

2values were noted 5min (T1), 10min (T2), 20min

(T3), 30min (T4), 40min (T5), 50min (T6), and 60min (T7)after tracheal intubation. The anesthetist who evaluated andrecorded the data was blind to the group allocation.

2.3. Statistical Analysis. The power value was evaluated withthe G-power 3.1 package program. An a priori power analysiswas based on previously published study [8].The sample sizeswere calculated on the assumption that a 20% difference inFEV1 and FVC was significant. In accordance with the powercalculation method, to demonstrate a 20% difference at 𝛼 =0.05 and a power of 85%, 30 patients per groupwere required.Statistical evaluation of the data was performed using SPSSver. 16.0 (SPSS, Chicago, IL, USA). Kolmogorov-Smirnov testwas used to identify the distribution of variables. Results areexpressed as mean ± SD or ratio of patients. Comparisonbetween the two groupswas performed usingMann-Whitney𝑈, Wilcoxon Sign Test, or paired 𝑡-test. The results wereevaluated at a 95% confidence interval at a significance levelof 𝑃 < 0.05.

3. Results

Three patients with lung disease, one patient with cardiacdisease, three smokers, and one patient switching fromlaparoscopic cholecystectomy to open cholecystectomy wereexcluded. Also two of the patients, who had operations lastinglonger than one hour because of surgical problems thatmay result in altering the postoperative pulmonary functiontests, were excluded. Sixty patients completed the study. Thedemographic data are shown in Table 1. The groups weresimilar in demographic characteristics.

No significant differences were found between the twogroups in terms of HR, MABP, SpO

2, and ETCO

2during

anesthesia. Although mean ETCO2levels in Group L were

BioMed Research International 3

Table 1: Demographic characteristics and findings.

Group H (𝑛 = 30) Group L (𝑛 = 30) 𝑃 valueAge (years) 44.77 ± 9.21 44.57 ± 9.87 0.936Sex (male/female) 3/27 3/27 1.000Weight (kg) 76.4 ± 9.42 75.9 ± 11.98 0.858Height (cm) 164.13 ± 7.08 163.10 ± 5.50 0.530Body mass index 28.56 ± 4.5 28.67 ± 5.12 0.927ASA class (I/II) 20/10 19/11 0.788Operative time (min) 47.93 ± 4.91 46.28 ± 18.5 0.787Values are expressed as ratio or mean ± SD.Group H: high-flow sevoflurane anesthesia group.Group L: low-flow sevoflurane anesthesia group.

Table 2: Comparison of the preoperative and postoperative forcedexpiratory volume in 1 s forced vital capacity and forced expiratoryvolume in 1 s/forced vital capacity values.

Group H Group L 𝑃 valueFEV1 (L)

Preoperative 2.85 ± 0.69 2.78 ± 0.54 0.643Postoperative 2 h 2.37 ± 0.73 2.22 ± 0.54 0.723Postoperative 8 h 2.44 ± 0.68 2.46 ± 0.54 0.865Postoperative 24 h 2.69 ± 0.78 2.72 ± 0.56 0.868

FVC (L)Preoperative 3.13 ± 0.74 3.10 ± 0.57 0.904Postoperative 2 h 2.51 ± 0.84 2.47 ± 0.48 0.756Postoperative 8 h 2.73 ± 0.77 2.69 ± 0.52 0.805Postoperative 24 h 2.95 ± 0.79 2.96 ± 0.55 0.952

FEV1/FVC (%)Preoperative 0.92 ± 0.10 0.90 ± 0.07 0.272Postoperative 2 h 0.93 ± 0.06 0.90 ± 0.08 0.074Postoperative 8 h 0.91 ± 0.09 0.92 ± 0.05 0.473Postoperative 24 h 0.91 ± 0.10 0.91 ± 0.07 0.988

Values are expressed as mean ± SD.FEV1: forced expiratory volume in 1 s.FVC: forced vital capacity.FEV1/FVC: forced expiratory volume in 1 s/forced vital capacity.

higher than those in Group H, the difference was notstatistically significant. Higher CO

2levels did not result in

clinical complication in any patient.Preoperative and postoperative pulmonary function test

results were similar in both groups. In all patients, the FVCand FEV1 values were significantly decreased in all measure-ments in the postoperative period compared to preoperativevalues, and this decrease was most pronounced during thesecond hour of the postoperative period. We also comparedthe postoperative FEV1/FVC ratio to the preoperative valuesand found no statistically significant differences between thetwo groups (Table 2).

There was not any contamination whereby the protocolswere altered for any patients in either the low-flow or thehigh-flow groups with regard to the intervention specificallyduring the procedure. None of the patients complained aboutany side effect of anesthesia or its complications.

4. Discussion

The present study shows that the effects of low-flow sevoflu-rane anesthesia on pulmonary functions in patients under-going laparoscopic cholecystectomy were comparable to theeffects of high-flow sevoflurane anesthesia. Laparoscopiccholecystectomy is often used as an alternative to laparo-tomy due to its advantages, including shorter hospital stays,earlier mobilization, smaller incisions, a low incidence ofpostoperative pain, and less need for analgesics [5, 6]. Duringlaparoscopic cholecystectomy, as a result of CO

2insufflation,

intra-abdominal pressure is increased, the movement of thediaphragm is restricted, and the functional residual capacity(FRC) is decreased. Hypercarbia can also occur due todecreased FRC and CO

2absorption [6, 7]. Baraka et al. [7]

reported that, during the laparoscopic interventions, end-tidal CO

2showed a progressive increase following induction

when the ventilation parameters were constant. Low-flowanesthesia has some disadvantages, such as hypoxia, overdoseof anesthetic agent, and hypercapnia [9]. At the onset of low-flow anesthesia, the clearance of nitrogen from the bloodby giving high-flow 100% O

2ventilation for 10–20 minutes

ensures an easier distribution of the anesthetic gases into thesystem and a more convenient adjustment of the gas con-centrations. It has been demonstrated that the replacementof nitrogen with oxygen in the lungs increased the oxygenreserve and thereby the apnea time [10]. In our patients,although ETCO

2levels during the low-flow anesthesia period

were found to be higher in Group L than in Group H,the difference was not statistically significant, and increasedCO2levels did not result in clinical complications. With a

decreasing flow rate, the difference between the concentra-tion of O

2in the fresh gas mixture and the concentration of

O2in the inspired air is increased. If low FiO

2is inspired

during rebreathing, a potential risk of hypoxia occurs. Todefinitively prevent hypoxemia and to ensure a continuousand adequate O

2presentation, the concentration of O

2in

the inspirium should be at least 30% [10]. Okada et al. [11]in their low-flow anesthesia sevoflurane study found thatthe difference between FiO

2and O

2increased with time as

the inspired oxygen concentration (FiO2) values increased.

However, reductions in FiO2to less than 30% were not seen

in any patients in the two groups.In our study, we used a mixture of 50% O

2and 50% N

2O.

The concentration of O2in the inspired air was monitored.

In none of the subjects did FiO2fall below 42% during

the operation. Although decreases in the concentration ofinspired and expired O

2were observed, it never fell to a

clinically significant level.As inspired and expired gases are mixed during the

administration of low-flow anesthesia, the concentration ofinspired gas is not directly correlated with the settings ofthe vaporizer. One of the important dangers of the low-flow anesthesia technique is the elevation of circulating theanesthetic concentration to levels so much higher than theconcentrations set in the vaporizer [12, 13]. However, duringthe administration of low-flow anesthesia, it is not very likelyto reach a high concentration in a short period of time,even if the settings of the vaporizer are erroneous, because

4 BioMed Research International

the concentration of the anesthetic agent is slowly increasedin the continuously breathed air in the pulmonary tract.Unlike high-flow anesthesia, a careful clinical observationmay serve to determine the erroneous settings before seriousand probably dangerous changes have occurred.

During low-flow anesthesia, the ventilation pressure maychange.Negative pressuremay occur and tidal volumemay bedecreased. In the studies performedwith low-flow anesthesia,ETCO

2was maintained between 30 and 35mmHg. Sajedi

et al. [14] did not find any difference in the SPO2and ETCO

2

values with low- and high-flow anesthesia in laparoscopiccholecystectomy patients. In our patients, ETCO

2varied

between 26 and 40. As the change of ETCO2did not cause

a change in SPO2or any hemodynamic parameters, we did

notmake any changes to the tidal volume and pulmonary ratesettings.

In the techniques of low-flow anesthesia, vector gasesand volatile anesthetics are known to provide considerablecost savings due to the decreased amount of wasted gas.In previous studies, it has been reported that 80–90% ofanesthetic agents and gases are wasted with a flow rate of5 L/min [15].

In low-flow anesthesia, it is easier to maintain theanesthetic depth previously obtained in volatile anaestheticswith low solubility, such as desflurane and sevoflurane.Furthermore, when high-flow is used, some issues maybe encountered with the agents that react with dry CO

2

absorbents, such as desflurane, enflurane, and sevoflurane[16].

The preservation of hemodynamic stability has beenproven by some researchers in recent low-flow anesthesiastudies [17–19]. In our study, hemodynamic stability was pre-served and no significant difference in results was observedbetween the groups.

Physiological changes during general anesthesia couldlead to postoperative pulmonary complications. A decreasein FRC leads to a disruption in the balance between ventila-tion/perfusion and hypoxemia. A decrease in postoperativevalues of VC and FRC has been shown in many high-flow anesthesia studies which investigated postoperative pul-monary function tests after abdominal surgery [20]. Rockand Rich [21] showed a decrease in FVC and FRC afterupper abdominal and tracheal surgeries. In another study,preoperative and postoperative FVC, FEV1, and FEV1/FVCvalues were measured on the first and sixth day in open andlaparoscopic cholecystectomy patients and it was shown thatin open cholecystectomy patients FVC, FEV1, and FEV1/FVCvalues were lower than in the other groups [22].

A few groups have studied the effects of low-flow anesthe-sia on hemodynamic and pulmonary functions and in thesestudies isoflurane and desflurane were used as volatile anes-thetic agents [18, 23]. Bilgi et al. [1] compared FVC and FEV1levels after low-flow and high-flow anesthesia with desfluraneas the inhalation anesthetic agent and observed a decreasein FVC and FEV1 levels in both groups on the postoperativefirst day, but, in the low-flow anesthesia group, the decreasewas much greater than in the high-flow anesthesia group. Inour study, although postoperative FVC and FEV1 levels at the2nd, 8th, and 24th hours were lower than preoperative levels,

there was no statistically significant difference between thetwo groups (𝑃 > 0.05). The decrease was markedly higher atthe 2nd hour than at the 8th and 24th hours. The causes ofa significant decrease at the 2nd postoperative hour may bedue to a prolonged effect of myorelaxants or recurarisation,postoperative pain, or increased abdominal pressure due tointraoperative-caused pneumoperitoneum.

Our facility is not enough because the study has limita-tions. It would be useful if we had measured the gas leveland the heat/humidity after the “Y” piece. But we could notdo it. If high- or low-flow anesthesia is applied properly,no different gas composition and no pressure or volumechanges after the “Y” piece are found. But when it is notused with care, it can affect both oxygenation and ventilationand can cause serious damage to the patient. When weuse low-flow anesthesia, it can better preserve heat andhumidity compared to high-flow. This difference can impacton pulmonary functions as well. But this kind of harmingeffect needs time to be meaningful. In this study, averageoperating time is approximately 47min so that is enough toaffect the pulmonary functions. Fortunately, we did not seethe effect on pulmonary functions.

Consequently, neither the low-flow sevoflurane groupnor the high-flow sevoflurane group showed any significantchange in pulmonary functions postoperatively. In lightof these findings, we conclude that low-flow sevofluraneanesthesia, without any adverse effect, may be administeredfor laparoscopic abdominal surgery.

Competing Interests

The authors declare that they have no competing interests.

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